Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$185.29	7.142%	$198.5234	$198.52	$198.50	$198.50
Purchase #2	$51.78	4.113%	$53.9097	$53.91	$53.90	$53.90
Purchase #3	$64.29	12.306%	$72.2015	$72.20	$72.20	$72.20
Purchase #4	$173.44	4.184%	$180.6967	$180.70	$180.70	$180.70
Purchase #5	$184.49	3.123%	$190.2516	$190.25	$190.25	$190.30
Purchase #6	$234.84	12.452%	$264.0823	$264.08	$264.10	$264.10
Purchase #7	$21.77	12.754%	$24.5465	$24.55	$24.55	$24.50
7 purchase totals =	$915.90		$984.2117	$984.21	$984.20	$984.20